<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<script>
    const arr = [1,2,3,4,5,6,7];
    const sum = arr.reduce((pre,item)=>{
        return pre+item;
    },0)
    console.log(sum);
</script>
<body>
    
</body>
</html>